In certain industrial applications, there is a need for alloys which possess high rupture strength and high oxidation resistance at high temperatures. Among such applications are those involved, for example, in the glass fiber industry, where filaments are produced by passing a molten material, for example glass, through the foraminous walls of a chamber adapted for rotation at high speeds, the chamber being known as a spinner, the filaments being emitted through the apertures of the wall due to the centrifugal action to which the molten material is subjected upon rotation of the spinner. Such spinners are usually operated when spinning glass fibers at temperatures of about 1121.degree. C. (2050.degree. F.) and rotational speeds of 2,100 RPM.
Structural components such as those at elevated temperatures under constant loads experience continuous dimensional changes or creep during their lives. This creep behavior depends upon the interaction between the external conditions (load, temperature) and the microstructure of the component. In recent times, increased resistance to creep of material systems has been accomplished by using a dispersion of very small, hard particles (called dispersoids) to strengthen the microstructure of the component. Further improvements in strength are obtained through controlled thermomechanical processing to develop a coarse grain structure. Such a structure is required to prevent grain boundary sliding during high temperature service. In the case of a spinner for fiberizing molten glass, biaxial loading is experienced, and a coarse pancake grain structure is required. These systems have come to be known as dispersion-strengthened metals and alloys, and the dispersoids used are usually oxides.
A recent development in dispersion-strengthening has resulted from a process known as mechanical alloying. Generally, the process uses a high energy ball mill to achieve the intimate mechanical mixing typical of the process. An attritor mill or vibratory mill also can be used. The desired coarse grain structure in wrought products is obtained through a series of thermomechanical processing steps such as extrusion, hot rolling, forging, and hot spin forming followed by heat treating.